In the disclosure of the present invention reference is mostly made to the treatment of diabetes by subcutaneous drug delivery, however, this is only an exemplary use of the present invention.
The most common type of durable drug delivery devices adapted to receive a drug-filled cartridge and expel a set dose therefrom are driven by manual means or by a spring energized during dose setting, the cartridge being of the type comprising an axially displaceable piston having an initial proximal position. Subcutaneous drug delivery takes place via an injection needle arranged in fluid communication with the cartridge. The device may be pen-formed or in the form of a more box-shaped so-called doser. In order to improve convenience, user-friendliness and provide additional features, e.g. detection and storing of expelling data, drug delivery devices have been provided with electrically driven means, typically in the form of an electronically controlled motor driving a piston rod through a gear arrangement, e.g. as shown in U.S. Pat. No. 6,514,230 and US 2011/306927. The same arrangement is also used in infusion pumps, e.g. as shown in U.S. Pat. No. 7,193,521. To drive the motor and the supporting electronics such a drug delivery device is provided with a power source in the form of one or more “batteries” (electric cells). In an infusion pump the batteries are typically standard disposable batteries whereas in a motorized pen-type drug delivery device the battery is typically build-in and rechargeable, e.g. as used in the “pendiq” digital insulin pen manufactured by Diamesco Co. Ltd, Daejeon, Korea.
However, a build-in battery will typically be charged using an external charger adapted to be connected to a wall power outlet supplying e.g. 110 or 220 volts. If the connection to an external charger is done via a wired connection, there may be a potential risk of electrocution to a user if the user were to attempt to use the device while the device was still connected to the external device. For instance, an internal fault or fluid leakage within the drug delivery device could bypass the electrical insulation measures of the device and allow direct connection between the power source and the user.
Addressing this issue, US 2013/0079708 which is hereby incorporated by reference discloses rechargeable drug delivery devices configured such that an administration of the drug is prevented while the device is connected to an external charger. More specifically, US 2013/0079708 discloses a number of different designs in which it is physically prevented that a charger can be connected to the drug delivery device unless the device is in a “mechanical state” in which drug delivery is not possible.
Having regard to the above, it is an object of the present invention to provide a motorized drug delivery device which provides a high degree of safety in a cost-effective and convenient way.